Apparatus for cracking hydrocarbons



J. E. BELL ET AL.

APPARATUS FOR CvRACKINGl HYDROCAHBONS Sept. 6, 1927.

FiledJuly 25,

1925' 5 sheets-sheet 1 u Y 1,641,941 SPt 6 1927 J. E. BELL ET Al. y

APPARATUS FOR CRAGKING HYDROCARBONS 1 v il' 6 1927. ,641,941 Sept J. E. BELL ET AL APPARATUS FOR CRACKING HYDROCARBONS Filed July 25, 1925 5 Sheets-'sheet 5 l 14541,@41' Sept- 6 1927' J. E. BELL ET Al. y

APPARATUS- FOR CRACKING HYDRQCARBONS vFiled July 25, 1925 5 Sheets-Sheet 4 fw i ATTORNEYS i Sept 6"1927 V.1. E. BELL ET A1.

AEPARATUS FOR CRACKING HYDRCARBONS Filed July 25, 1925 5' sheets-snee; 5

f AToRNEYs JOHN E. BELL-LECEAsEn, LATE `or BROOKLYN, NEW YORK, BY LoLA n. BELL, EXECU- TBlX, F BROOKLYN, NEW' YORK, AND EDWARD W. ISOM, OF LOCUST VALLEY,

NEW YoBK',-Ass'1eNoKs Iro srNcLam nE'INING ooMPANY,oE NEW YORK, N. Y., A

CORPORATION 0F MAINE.

ArPA'na'rUs Een cnAcKINe nY'nnocaanoNs.

. Apncunmeaiuiy 25, 1925. serial No.`45,97e.

This inventiony relates to improvementsin apparatus forl cracking 'heavier hydrocarbon oils, such as gas oil, forthe yproductionof llighter hydrocarbon oils, such as gasoline 6 .or pressuredistillate, by distillation under This application is in part a conpressure.

the process of an application led March 111,4

'l5 1925, Serial No. 15,459.

In cracking hydrocarbon oils by distillation under pressure, the oil is heated to a cracking temperature under pressure and the` heavier oil, or `a portion thereof, is broken down or c'rackedl with the formation oflighter'oils which are vaporized and driven off. The" cracking operation takes -place gradually and rogressively, part of the @racked constitue ts escaplng as pres- 95 sure distillate. and partv ofI the heavier cracked constituents remaining and mixing Withthe charge of oil in the pressure still. A small lamount ofasphaltic, or pitch-like constituents, or heavy tar is also formed by the cracking operation. This tar remainsin the charge and gradually accumulates due to the vaporizationof cracked constituents and to the progressive formation of tar constituents. This tar .accumulating in the oil in the still tends :to deposit on the heating surfaces vof the still and in contact therewith tends toform'a carbonaceous depositthereon ,closely adhering thereto. Such carbonaceous materials and the heavy` tar accumulat- 40 ing .in the still charge arepoor conductors of lheat and when depositedon the heating surfaces of the still which are externally ex posed to heating gases interfere with heat transfer and vinsulate the wall from the protection afforded bythe oil sdthat the Walls of the still Vare apt to become overheated, the temperature of the metal' ofthe Aheat transferring wall increasing over that of the oil to an extent 'dependent upon the thickness 50 of the deposit andthe amount of heat externally delivered to the wall from the heating gases. As a consequence the pressure still must frequently be shut down for cleaning or 'the temperature of the heating gases must be'educed below that which is most efficient.` There is also considerableA danger involved due. to possible bursting of the heat transferring walls at overheatedpoints.

*The heating surfaces over which heatinggases are first circulated are exposed to the -highest temperature of the-heating gases and absorb the greatest amount .of heat, and` these surfaces are most apt tosuifer.- -Heata L94,- STATES PATENT "oFF'IcE.

ing surfaces immediately adjacent thfuri.

nace employed t0' heat the pressure still may`f5- also absorb a large amount of heat by direct radiation .fr oni the furnace.

According to the presentinvention,tl1e

heating surfaces of the pressure still are protected in a dual manner, both by regulat-*Y ing the characterof the oil charge in contact with the heating surfaces and by regulating the temperature. of the heating gases. The regulationof the character of the o'il chargegiscarriedout to prevent or reduce the accumulationoftar in the oil in Contact .with` the heating surfaces over which' the heatingv gases are first circulated, that is the heating surfaces.in contact with the hottest heating gases, and .the regulation of -the temperature of the heating gases is'carried out :without decreasing either the capacity or efficiency of either the still or the heating furnace by returning part of the heating.y gases which have passed over the heatingfA surfaces and adniixing them with the fresh` heating gases first circulating` over the heat-` lng surfaces. This dual regula-tion, -in acacordance with the presentl invention, also provides twol vmeans of controllingthe heat-` lng operation, and consequently the cracktai ing operation. This dual regulation valsovr enables animproved operation of the pressure still in the treatment of diHerent charging stocks and for the production of products of varying' characteristics. #By returning heating gases at approximately the temperature at which they are` vdischarged from lthe heating surfaces and admixing them with fresh heating gases from the furnace, thefresh `heating' gases arertempered without however reducing the eiiiciency or capacity of the heatingoperation. The temperature of theheating gases first contacting with ythe heating surfaces can thus be reduced in an eicient manner l heating gases are first passed, the heating element of the next compartment B in the vlue 9, and so on,the heating element connected'to the last compartmentl D being arranged in the last heating flue 11. through which the coolest heating"`gases are circulated. The artitions in the drum do not completely' ut oil the compartments from each other but extend ashort distance above the-'normal liquid level therein leaving a` common vapor space inthe upper part of `the drum. Overflow pipes 16, 17 and 18 are arrangedfor progressively .transferring oil tov successive compartments in the series,

and these pipes are provided with bell caps, to prevent transfer of surface `scum froth to successive compartments. Ar-L and ranged above the drum 6 is a reflux tower 19 adapted to receive vapors from the vapor space of the drum 6 and tofdischarge reflux,"

3" and any admixed oil, into the first compartment A. lA connection 20 is provided for introducing freshl o il into the vupper ,part of the reiux tower, and a connection 21 is provided for introducing fresh oil directly into the irst compartment A. The vapors escape from thereflux towerthrough vapor line 22 to a condenser diagrammatic'ally illustrated at 23.y The pressure in the still may be reduced and controlled by a regu- 0 lating valvev 24 arranged between the reflux tower and the condenser orby a valve 25 arranged be ond the condenser. The reflux tower and t e still drum may,'with advantage, be covered or' protected with suitable 5 heat insulation, suchas an asbestos or mineral wool jacket.

To the extent described above, the pressure still illustrated in Figs. 1 and 2 is of construction similar to that illustrated in 0 Figs. 3, 4 and `5 and corresponding parts in Figs. 3, 4 and 5 aredesignated by the same reference characters with'the letter a appended. The pressure still illustrated in Figs. 1 and 2 is arranged so that .circulation is maintained by convective action,

while the pressure still illustrated in Figs. L3, 4 and 5 is arranged so that circulation .is maintained by mechanical forcing means o such as pumps.

Again referring to the pressurel still illustratedin Figs. 1 and'2, each ofthe heating elements connected to the respective compartments comprises` three similar groups `of heating tubes. Each of these groups comprises an outflow header 26, a

series of upwardly inclinedv tubes 27 arranged through the heating' liue for heat 'exchange with' the heating gases therein,

connecting headers 28, another series of upwardly inclined tubes arranged-through the heating flue, and an inflow header 30. In order to facilitate cleaning and-repair the headers are arranged outsideofthe heating fines and are formed with plugged hand holes in alignment with the heating tubes` In order to equalize the heating effect in the several heating elements and to provide an'v increased area of heat transfer as the 'tar content lof the oil increases, the heat transferring area of the several headers is progresslively increased as thetempera'ture of the heating gases declines. In the still il-A lustrated, the headerconnected to the irst compartment A has four tubes in each group, that connected to compartment' B eight tubes, that connected to compartment C twelve tubes, and that connected-to the last -compartmentD sixteen tubes. in o'rderl to provide for drainage, and for withdrawal of 'tar during the cracking operation, the-lower 'ends of the linliow headers V in -eachiheatingelement are connected to a manifold 3.1 having aivalved outlet 32, the

outlet from the last compartment D being designated 32. Al draft tube 33 is arranged for withdrawing waste heating gases from a point adjacent the'exit of the heatelement connected .to the last compartment D is arranged, land returning them to the ing au@ 11, the flue in which the heating flue 8 for tempering the heating gases fresh' from the furnace 7 in the flue 8. The draft' tube may be operated by a steam jet or other suitable forcing means. By-passes 34 and 35 provided lwith regulating dampers 36 and 37 are provided for further controlling the distribution of heat in the several flues.

In the pressure still illustrated in Figs. 3,4v and 5, the-heating elements vconnected to the respective 4compartments also comrise three similar groups of heating tubes.

ach of these groups comprises a header 38, a series of upwardly inclined tubes 39 arranged through the heating flue, connecting headers 40, another series of upwardly inclined tubes 41 arranged through the heating flue, "and a header 42 discharging into the corresponding compartment in the drum 6a. The headers 38 in each group areconnected to a common'hoiizontal header v43 which is in turn connected through pipe 44 to the discharge side of a circulating pump'.

A connection 45 is also vprovided between eac'h compartment in the drum and the inlet. side of the circulating pump ldischarging Lasv through the header connected to that coi-Y partment. A separate lpurnpjmay be emmon caslng and driven by a common driv-j ing means as shown in the drawings. The pumps shown in the drawings are of the rotary pistou type, sometimes known as Uonnersville pumps and are particularly adapted for use in carrying out the process of the invention but it will be apparent that pumps of other suitableconstruction adapted to handle hot oil at the cracking temperature may be employed. The pumps shown are independent and the oil is separately circulated through each ofthem, par-A titions being arranged between the several pum) chambers` to confine the oil in each circu ating stream to that stream. A valved outlet 4G is provided in the connection 4l' to the last compartment for discharging tar from the pressure `still during the cracking operation. A draft tube-47 is arranged for withdrawing waste heating gases lfrom a point adjacent thc exit of the heating flue vll and returning them to the flue 8 for tempering the heating gases fresh from the furnace 7 in the flue 8*. The draft tube may be operated by asteam jet or other suitable lorcingrnicans. By-passes provided with dampers may also be arranged between the heating lines 8, 9 and 10 as described in connection with the pressurefstill illustrated in Figs. l and 2.

It will be apparent that, in each construction illustrated, the oil supplied to the still is first brought in heat exchanging relation with the heating gases of highest temperature and as the tar concentration of the oil increases the oil is progressivey brought in heat exchanging relation with` heating gases of lower temperature and that, at the same time, the heating gases are temperedbefore first being brought in heat exchange with the oil by recirculation of a part of the waste heating gases. The heating surfaces of the pressure still are thus protected in a dual manner, beth by regulating the character of oil charge in contactvwith the heating surfaces and by regulating the temperature ot Y the heating gases. The area of heating surface of the heatingm elements may lalso be increased as'the temperature of the heating gases declines and as the tar concentration ot' the oil increases. further protecting the heating sui-'faces of' the pressure still.

In thc operation of the apparatus illustrated. the stil is initially charged with oil through connection 2l. or connection 21a, the oil successively overilowing Vinto the adjacent compartments as the preceding compartments kand heating elements are filled, and the still charge is then brought to the cracking tcnnzerature and pressure in the usual way. 'lhc pressure employed may differ with diilcrcnt charging stocks and Afor the production of different pressure distillates. lilith gas oil character charging stocks 'for the production of gasoline character distillates, pressures in the neighbor- Let-1,941

hood of 90to 125 lbs. per sq. in. or more may be employed. In cracking kerosene character charging stock to produce a gasoline character distillate, considerably higher pressures may be used, for example, pressures up to 800 lbs. per sq. in. or more .may be employed. 4

After the still charge is brought to the cracking temperature and pressure, the cracked vapors rise from the several compartn'ients and pass upwardly through the reflux tower 19, or 19a and the introduction of fresh oil into the reflux tower in direct Contact with the va ors therein is begun. In the reflux tower, tie fresh oil is intimately contacted witlrthe vapors from the still, I'e- Vlluxing' the heavier vapors and preheating the fresh oil, and the reflux and admixed fresh oil are returned to the first compartment A. Additional* fresh oil may also be supplied through connection 21, or 212 As reflux and freshoil are supplied to compartment A, oil from this first compartment which has been deprived of part of its crackablecnstituents and contains some tar constituents overflows inte the second compartment B where it is further cracked and a further part of its components are vaporized. In the same way oil is transferred from compartment B to compartment C and from compartment C to compartment D as the cracked constituents-are vaporized. and as the tar accumulates, the oil in thesuccessive compartments containingless and less o' the original Voil constituents and more and more hea tarry constituents. The supply of frcs 1-oil and reflux to the first compartment also assists in maintaining a low tar concentration in the oil therein. The introduction of fresh oil into the reflux tower may be controlled to regulate the relluiting 'introduced partly into the reflux tower and partly into compartment A directly, or it may a`l be introduced directly into compartment A. y

Theheating gases from the furnace 7, or 7, are passed successively over the heating elements connected to compartments A, B, C and D in order so that the oil in the first compartment A, including the refluxand fresh oil supplied to this compartment, vis subjected to the highest temperature, that in thc second compartment B to a somewhat lower temperature, and so on. However, before the heating grecs fresh from the furnace are passed over the-heating element connected to compartment A, they are temfurnace.

, ing

ered byfthe admixture therewith of vWaste lieating gases withdrawn from the last heatiiue and returned and admixed With'the fresh products of combustion leaving the This tempering of the hottest heating gases assists in protecting the initial heating surfaces in the heating element connected to compartment A and these heating surfaces are further protected by the ab.-

by the recirculation of part of the circulating gases and by the absorption of heat in the heating elements connected to compartmentA s o that as the tar content of lthe oil increases the temperature of the 'heating gases declines, while the heating surfaces' exposed to the hottest lie'atingigases arejprof' tected by the circulation thereover 'off'ollif containing the least content oftar. lnrgllgf the'heating elements the absorption of heat `0 hea-ting iiues communicating With a fire 9,5. i

by the circulating oil protects the heating surfaces, and particularlydnthefirst Where the heating element is exposed tothe hottest heating gases and where the circulating oil contains the vrefiux and the fresh oiland the least content of tar. As tar accumulates v in the oil it is further cracked for the-further recovery of the desired 'pressuredistillate but by heat exchange -vvith heating' gases progressively declining in temperature as the tar content of theoil increases.

i It will thus be seen that the present in-Y vention provides an improved apparatus lfor cracking hydrocarbon oils by distillation under pressure in externally heated pressure stills in which the heating 'surfaces'of "constituents accumulate therein the oil is circulated over heat-ing surfaces exposed to the cooler'heating gases from the preceding heatingof oil having a'lovver 'tar' content. The apparatus of thev invention has several important advantages. It enables the cracking operation to be carried out for a longer period Without decrease in the rate of cracking. fItalso enables an improved application of the heating gases to the cracking operation so that'both` the efficiency and capacity of the pressure still' may beinc'reased. I Further, it affords improved protection to the heating surfaces of the A.pressure still particularly to the heating surfaces which are exposed to the most intense heat and to 1 the severest conditions.

-We claim: l. In an oil cracking still, a drum,`par

titions in the drum dividing thesame into communicating compartments, meansv for feeding'the oil into the compartment at one end of said drum, a furnace having a series box,` heating units connected to the respective compartments and progressively 'arrangedin the flues, the heating unit con-i nected to the 'supply compartment being nearestthe fire box, and means for returning aV portion. of the' products of combustion from a point in the heatingiiues more remote from the-fire box -in the furnace to a .point less remoteftherefrom. i l

2. Inan oil cracking still,a drum, partitions in the `drum dividin'g the sameinto communicating compartments, ymeans for feeding'oil into the compartment'at one end of said drum, a furnace having successive communicatingvflues corresponding t'o said compartments communicating With a re f the still are protected both by recycling part LbOX, heating units Connected to the respecfirst Contact, that is the surfaces subjected Y.

"of the waste heating gases from the still and 4 employing them to temper the fresh prod-- ucts of combustion from the furnace and by supplying fresh oil and reflux to that part of the oil charge circulating over the heating surfaces wlth which the heating gases to the hottest heating gases, so that the oil circulating over theseA initial heating surfaces contains a `low content of tar. The heating gases cooled and tempered in this initial heating operation and by the temper-v ing due to the recirculationY of Waste heating gases are then employed to further heat andcrack the oil as cbon and tar constituents accumulate in it. The oil circulated over the initial heating surfaces thus contains the highest proportion of fresh oil and reiux constituents, and at the same time in -the respective heating iiues, lthe heating unit connected to the compartment towhich oil is supplied being arranged in the heating` flue nearest the fire box and means for drawing a portion of the 'products of combustion from the heating flue most remote from thev iire box and returning it to the heating iiue nearest the fire box. `1 3. In an oil cracking still, a furnace having a heating iiue communicating at one end with a lire box, a drum adapted to contain a charge of oil, heating means arranged in the heating iue and connections for circulating oil from and to the drum therethrough, a separate heating means communieatin with the drum arranged in the heati ing ue betvveen the first mentioned heating plying fresh oil to the still, means for initially circulating the fresh oil through the last mentioned separate heating means, and means for recirculating through the heating flue part of the heating gases Which have passed over the heating means of the still.

Il. In'an oil cracking still, a furnace having a heating fine communicating at one end with a fire box, a drum adapt-ed to contain a charge of oil, a reflux tower communicating ivith the drum, heating means arranged in the heating flue and connections for circulating oil from and tothe drum therethrough, a separate heating means communieatin with the drum arranged in the heating ue between the first mentioned heating means` and the fire box, connections for supplying 'fresh oil to the still and connections for returning reflux from the reflux tower tothe still, means for initially circulating the fresh oil and the refiux through the last mentioned`A separate heating means,- and means for recirculating through the heating flue a art of the heating gases which have passe over the heating means of the still.

5. In an oil cracking still, a. furnace havi ing a heating Hue communicating at. one end iso with a fire box, a drum adapted to contain a charge of oil, a-reflux tower communicating with the drum, heating means arranged in the heating flue and connections for eirculating oil from and to the drum therethrough, a separate `heating means communicating with the drum arranged in the heating 4this between the rst mentioned heating means and the iiije hex, connections for returning refluxl from the refiux tower to the still, means for initially circulating the reflux through the' last mentioned separate heatin means, and means 4for recirculating throng i the heatin Vfiile heating gases which havepassed over t ie heating means 'of the still.' ,A A i 6.111 an oil cracking still a furnace havin a heating tlue communicating at one end with a fire hon, a drum adapted to contain a charge ci oil, a reflux tower communicating with the drum, heating means arranged in the heating tlue'and connections 'for circulating oil from and to the drum there-l through, a` separate heating means communieating with the drum arranged in the heating flue between the first mentioned heating means and the lire hex, connections` for introducing fresh oil into the reflux tower, means for initially circulating the fresh oil and adniixed reflux through the last mentioned separate 4heating` means, and means for recirculating through the heating flue a -part of the heating gases which have passed through the heating units` connected to the` several compartments, the heating unit connected to the supply compartment being;Y

nearest to the furnace,y and means for returning a portion of the products ot' combustion froma point in the heatingiluc` more remote from the furnace* to-a point less' remote therefrom.`

8. In an oil ,cracking still, a drum having a series of communicating compartments,

therein, afurnace having-a heating flue, heating units 1n the iiue connected to the several compartments, means for supplying oil to be treated to one of saidcompartments'` and for causing it to flow' successively to the othercompartments, the heating unit connected to the supply compartment, being nearest the furnace, and the heating units connected to' successive compartments having 'y progressively increasing heat transferring' areas, and means yfor returning a portion ot the roducts of combustion from 'a point in the eating fluepmore remote in the furnace to apo'int less remote therefrom In testimony whereof We affix our signa-` tures.

LOLA R. BELL,

freoutr of the Laat TV'ZZ and Sleatament i of Jom E. Bell, Deceased.

EDWARD lV. ISOM. 

